Optical brightening of paper



I I we 3,475,190 Unlted StatCS P atfiflllo Ice Patented Oct. 28, 1969 3 475 190 Compounds of Formula I which can be used according to the invention have been described in French Pat- Fr Q BRIGHTENING OF PAPER ent No. 905,534 as textile brighteners.

er Erwm pettschen a Switzerland Both unsized paper particularly however sized printassrgnors to Gergy Chemical Corporation, Greenburgh, w d h i ll N.Y.,acorporat1on of Delaware 5 5 an o ograp 16 Paper as as card- No Drawing Filed Dec 2, 1966, 598,640 board can be brightened by the use of brighteners of Claims priority, application Switzerland, Dec. 10, 1965, QU l Both the l and also the Paper Surface can I t Cl C0 2111 1/ be brightened according to the invention; preferably the n ;D 24 paper 'is optically brightened by the surface coatin US. Cl. 106-210 7 Claims process. g

' In ,practice, the surface finishing of paper is performed by the following two methods:

ABSTRACT OF THE DISCLOSURE Paper is optically brightened by coating the surface (A) i n the so-called starch-size process inside the paof the paper with an amount to efiectively optically .per machine, e.g. inasizing press, or

brighten said paper of a liquor containing a compound of i e so-called P Coating Process, insidfi the formula: For out of the paper machine.

H21? slosH HOsS NH! Ar-HN NH-Ar wherein Ar represents an unsubstituted phenyl radical 1'=t flrCh-SiZe process a rd ng t (A), a Coator one containing non-coloring substituents; and Water g liq r s u ed which; P litl'ercontains, soluble salts of such compound. In the preferred embodi- 2.0 g. of optical brightener of Form l I d 50-100 3- ment, the phenyl radical is unsubstituted. of'degraded starch. In addition it can contain slight amounts of wetting agents, e.g. unsulphated or sulphated alkanol glycol ethers having an alkyl radical containing The present invention concerns the use of certain bis- 8 1.4 carbon atoms and having 1 to 20 ethylene oxy s-triazinylamino-stilbene-2,2'-disulphonic acids for the groups. optical brightening of paper, particularly by the surface For the pigment coating process according to (B), a coating process, the liquor usable for this purpose as well coating liquor is used which contains, per litre, e.g. 0.2- as, an industrial product, the paper having a content of I 5.0 g. of optical brightener of Formula I, 350-650 g. of these bis-s-triazinylamino-stilbene-2,2'-disulphonic acids. White pigment and, calculated on the amount of white In order to meet present day requirements, white unpigment used, 8-30% by weight of binder, (ll-0.6%v sized and, apticularly, sized paper needs optical brightenby Weight of metal binding agents and 0.0l0.03% by ing. This whitening can be performed by treatment of weight of wetting agents. the pulp with substantive optical brighteners; advarr- Examples of white pigments are aluminum-magnesitageously however, for the brightening of paper, the so- 40 um silicate (China Clay), CaSO .l0H O (Satinweiss),

called surface coating process is used, as this process BaSO (Blancfix), titanium dioxide, optionally also enables the optical brightening and the surface finishing CaCO or mixtures of such compounds. to be performed simultaneously. However, the usual Examples of binders are dispersions of synthetic resins brighteners used for the surface coating process do not such as those based on butadiene-styrene, acrylic or methalways meet the increased whitening requirements beacrylic polymers or copolymers, together with degraded cause, generally, they are not sufiiciently active and, in starch, or dispersions of synthetic resins with casein, or high dosages, give the paper an undesirable greenish such dispersions together with degraded starch and tinge. casein.

It has now been found that bis-s-triazinylamino-stil- Examples of metal binding agents are water soluble bene-2,2'-disulph0nic acids of general Formula I, particu- 5 0 polyphosphates or polymetaphosphates, and examples of larly in the form of their soluble salts, are well suited for wetting agents are unsulphated or sulphated higher althe optical brightening of paper including cardboard, in kanol-polyglycol ethers such as those mentioned in the particular in the surface coating process. previous paragraph.

H21? SOaH IIIH;

Ar-HN HOaS NH-Ar In this formula, Ar represents the unsubstituted phenyl In order to obtain good rheological properties, prefradical or one containing non-colouring substituents. 'erably an alkaline coating liquor is used for pigment Examples of non-colouring substituents are the sulphonic coating. The alkaline reaction is advantageously adacid or carboxylic acid group, halogens such as fluorine, ju-sted with ammonium hydroxide or with sodium or chlorine or bromine, low alkyl or alkoxy groups which 5 potassium hydroxides, carbonates, borates, perborates or contain, e.g. 1 to 5 carbon atoms. Preferably, Ar is the mixtures thereof. phenyl radical. Paper is advantageously coated with these liquors ac- In particular the alkali, alkaline earth or ammonium cording to (A) and (B) in a painting apparatus used for salts, e.g. those derived from ammonia or an alkanolthis purpose. In this way papers are obtained which, in amine, are used as soluble salts. The disodium salt is addition to an improved surface, have a more white and preferred. pleasant appearance.

EXAMPLE 1 Bn'ghtening in the starch-size process The 2 g. of optical brighter of the formula as disodium salt are dissolved in 40 ml. of 90 hot, dis tilled water.

Also 80 g. of a degraded starch (e.g. Noredux l, Blattmann Co., Wiidenswil, ZH, Switzerland) in 1000 ml. of 90 hot water are made into a colloid suspension over a period of minutes.

The brightener solution is then incorporated into the starch solution. The solution obtained containing starch and brightener has a pH of 5.5 to 6.0.

The surface of a sized paper for printing is coated with this liquor in a sizing press and the coated paper is dried at about 50120 in the drier section of the paper machine.

In this way a paper is obtained the degree of whiteness of which is considerably improved.

Instead of sized paper, sized cardboard can be used with the same result.

Similar results are obtained under otherwise the same conditions if, instead of the brightener given above, a brightener of similar structural formula is used which, instead of the phenyl substitutent corresponding to Ar in general Formula I, contains one of the radicals:

4 EXAMPLE 2 Brightening in the pigment coating process 3.5 g. of the optical brightener given in paragraph 1 of Example 1 are dissolved in 40 ml. of hot, distilled water. 1000 ml. of an aqueous coating liquor are then added to this solution, which liquor contains the following components: Usual commercial casin g 45 A dispersion of synthetic resin containing about 50% synthetic resin, based on butadiene-styrene polymers (e.g. Dow-Latex 636, Dow Chem. USA) g 70 Sodium polyphosphate g 2 Sulphated dodecyl alcohol polyglycol ether having 15 ethylene oxy groups ml 0.2 Aluminum-magnesium silicate (China clay) g 400 Concentrated ammonia ml 12 The pH of this dispersion is about 9.0.

The surface of sized paper or cardboard is coated with this liquor in the sizing press or another device.

A paper coated extraordinarily white is obtained.

EXAMPLE 3 Brightening of paper pulp 50 g. of an aqueous suspension of bleached sulphite cellulose containing 5 g. of absolutely dry cellulose are mixed with ml. of Water and the mixture is stirred well at room temperature. 0.71 ml. of a sizing solution 1:10 is added and the whole is again well mixed. 5 mg. of the optical brightener described in paragraph 1 of Example 1, dissolved in 10 ml. of water, are then mixed in, the mixture is again stirred Well whereupon the brightener completely draws onto the cellulose fibres. 1.5 ml. of aluminum sulphate solution 1:10 are then added to the pulp which is subsequently diluted with Water to 1000 ml.

The diluted pulp is made into sheets, pressed and dried. In this way a clear, white sheet is obtained.

Similar results are attained when the brighteners mentioned in the last paragraph of Example 1 are used.

We claim:

1. An aqueous coating liquor for the optical brightening of the surface of paper, said coating liquor comprising, per liter,

(a) 0.2 to 2.0 g. of a compound of the formula:

3,475,190 6 (ii) water soluble salts of the compound (i); and (a) 0.2 to 2.0 g. of a compound of the formula: (b) 50 to 100 g. of degraded starch.

S 3 S0311 NH,

2. An aqueous coating liquor for the optical brighten- (ii) water soluble salts of the compound (i); and ing of the surface of paper, said liquor comprising, per 15 (b) 50 to 100 g. of degraded starch. liter: 5. A method as claimed in claim 4 wherein the com- (a) 0.2 to 5.0 g. of an optical brightener of the forpound is -disodium 4,4'-bis[(4-anilino-6-amino-l,3,5-trimula: azine-2-yl)-amino]-stilbene-2,2'-disulfonate.

H N S0311 S0 11 NH;

(ii) water soluble salts of the compound (i); 6. A method as claimed in claim 4 wherein said liquor (b) 350 g. to 650 g. of a White pigment selected from comprises, per liter,

the group consisting of China clay, CaSO -10H O, (a) 0.2 to 5.0 g. of an optical brightener of the for- BaSO or TiO or mixtures thereof; mula:

HaN $0.111 S0311 NH! IIIH (c) 830% by weight of a binder based upon the Weight of Said Pigment; (ii) water soluble salts of the compound (i);

(d) 0.2 to 0.6% of a metal binding agent based upon 350 to 650 of a white pi selected from the weight of said pigment; and the group consisting of china clay, CaSO -10H O, (e) 0.01 to 0.3% of wetting agents based upon the BaSO or TiO or mixtures thereof;

Weight of Said Pigment (c) 830% by weight of a binder based upon the 3. coating liquor as claimed in claim 2 wherein weight f said Pigment; said binder IS a dispersion of a synthetic resm selected (d) 02 to 06% of a metal binding agent based upon from the group of butadiene-styrene, acrylic or methacrylic polymers and copolymers, and mixtures thereof welght of said plgmentiand (e) 0.01 to 0.3% of wetting agents based upon the with casein.

4. A method for brightening the surface of paper com- Welght of sald p f prising coating the surface of the paper with an amount A method as clalmed 111 (21211111 6 wherein the comto effectively optically brighten said surface of said paper Pound is disodium with an aqueous coating liquor comprising, per liter, azine-2-y1)-amin0]-stilbene-2,2'-disulfonate.

References Cited UNITED STATES PATENTS 2,376,743 5/1945 Wendt 106-162 2,213,643 9/1940 Acton 260-8 X FOREIGN PATENTS 529,326 8/1956 Canada. 862,851 3/1961 Great Britain.

JULIUS FROME, Primary Examiner T. MORRIS, Assistant Examiner US. Cl. X.R. 

